The present invention relates to a method and an electronic circuit arrangement allowing observation of bus-systems and networks. In particular the invention relates to such a method and circuit arrangement not causing electrical or physical constraints and influence to the bus-systems and networks. Still more specifically the invention provides for accessing static bus-systems and networks in particular used by real-time constrained systems and applications.
Buses and networks, used to interconnect real-time electronic systems, are typically defined during system definition and design. The number of bus attachments (loads) and, depending on the type of network to be accessed, the message IDs are predefined during the system definition and can not be altered during system runtime.
Typical representatives for real-time busses are for example networks used in today""s modern automobiles, like CAN (Controller Area Network), VAN (Vehicle Area Network), J1939 (specified by SAE, Society of Automotive Engineers) and others. The bus type, topology and the bus-participants are defined by the automotive manufacturer. For several reasons, it is not possible to add on additional devices or units to these busses after the vehicle left the manufacturing plant:
a) The most important factor is safety. Typically providing access to all major Electronic Control Units (ECUs) within the vehicle, safety relevant devices like brake control, engine management and others are connected to the real-time bus-systems;
b) The real-time bus-systems typically provide a limited amount of electrical drive capability, thus limiting the number of devices supported within one network.
c) The number of bus participants and accompanying addresses/message-IDs are kept to a minimum to allow to achieve cost effective systems.
As a consequence to the facts as explained, the busses are not xe2x80x98open to publicxe2x80x99, thus do not allow adding on new devices at a later time. Only by following this ground rule, the original manufactures will guarantee the vehicle operation to specifications, and most important, are liable to all safety relevant functions.
At present, this circumstance is a strong constraint to the further development of new after-market devices. Restricted by the status of bus access capabilities, these after-market devices are typically not supporting advanced applications demanding access to the vehicle real-time buses and networks.
Typical product examples are today""s after-market entertainment systems, navigation systems and telematics devices.
Nevertheless, new emerging applications like on-line services (entertainment, traffic information, etc.), real-time remote diagnostics, advanced xe2x80x98dynamicxe2x80x99 navigation systems and others are requiring access to data provided by the diverse vehicle sub-systems (wheel sensors, giro, speed, steering angle).
Due to the limiting facts as explained, this type of new services can only be offered by the original manufactures, provided as an OEM device, developed in cooperation with the vehicle developers.
Unless add-on-device bus access capability is not explicitly provided and built in by the vehicle manufacturer, after market devices are not supported and cannot be allowed to be added to the vehicle domain networks in a xe2x80x98plug and playxe2x80x99 mannerxe2x80x94an important security issue with potential legal consequences if ignored.
It is therefore an purpose of the invention to provide access to non-public, restricted networks as typically used in automobiles without the above mentioned shortcomings.
It is a further purpose of the present invention to provide a method having the most important features of the typical bus access methods, as known by standard network adapters.
The present invention describes a principle for an electronic control system providing access capability to protected networks and bus-systems for application processor units, especially used in an automotive vehicle. The active network access tool, in the following called Virtual Network Adapter (VNA) is exercised in a unique virtual manner, in real, the VNA network access is performing absolutely passively, thus not influencing the network neither logically nor physically, in particular there is no electrical influence.
Like standard bus-adapters/controllers, the VNA is featuring two access ports connecting to the external electronic systems. The primary side is accessing the protected real-time network in focus, while the secondary access port of the VNA is interfacing to the Controller System or ECU to be connected to the network.
As is known in the prior art, devices hooked up via standard bus controllers are actively writing to vehicle real-time networks. As for example the message xe2x80x98get oil temperaturexe2x80x99 will invoke a write command issued to the protected network, requesting the specified information from a specific vehicle domain ECU. Given this typical procedure, as normally executed by standard bus-controllers, therefore, the major requirement of not influencing the network cannot be fulfilled.
It is an advantage of the present invention that, although in reality not actively acting on the real-time network, the VNA system is supporting the major bus access functions like
Data/message on requestxe2x80x94invoked by external calling unit (xe2x80x98active bus access modexe2x80x99)
Data/message provision on pollingxe2x80x94invoked by external calling unit (xe2x80x98active bus access modexe2x80x99)
Data/message broadcastxe2x80x94VNA system initiated (xe2x80x98passive bus access modexe2x80x99)
The method proposed by the VNA principle is intended to provide access to the messages present at a given time to the most commonly used real-time bus systems. In order not to influence the existing (predefined) network for any reason, neither logically nor physically, standard bus controllers, using the typical arbitration and bus access procedures cannot be used.
As a consequence, not being able to arbitrate and to logically interfere with the respective bus participants, thus not being able to xe2x80x98requestxe2x80x99 required data on demand, in the xe2x80x98first thoughtxe2x80x99 leads to the conclusion, not providing the network access appropriate to the applications in mind.
The following important statement will provide the elementary precondition for the applicability of the VNA principle:
Each ECU, attached to a real-time network, will provide data and unit relevant information at the bus-system at a certain point of time. As a reversal conclusion: This fact not being the case would dispose the right for this unit to exist on the bus in the first place. In other words, each unit attached to the network will be providing data to the net, invoked on request by other units (regardless of technique, pooling or event triggered), or self-initiated, as for example triggered by an integrated sensor or any other internal logical event.
In any instance, the data providing messages will be issued and exposed to the network initiated by meaningful events and in adequate incidence.
Exactly this fact is the point of admission for the applicability of the proposed VNA systemxe2x80x94and in differentiation to feasibility, any network not showing to this basic attribute and behavior will not be meaningfully supported by the VNA.